Laser frequency stabilization using a spatially multiplexed microfabricated Rb vapor cell
Seji Kang, Soyeon Choi, Jaeuk Baek, S E Park, J Park, Yeeun Na, Taeg Yong Kwon, Sang-Bum Lee, Jae Hoon Lee, Sangwon Seo, Young‐Ho Park, Meung Ho Seo, Hyun-Gue Hong
Abstract We demonstrate a laser stabilization based on a spatially-multiplexed, microfabricated rubidium vapor cell. This design integrates multiple optical apertures within a cell, enabling a single input beam to simultaneously capture both Doppler-broadened and saturated absorption spectroscopy signals while a dedicated non-absorbing aperture directs the beam toward the physics package. We achieve a frequency stability of 4 × 10 −13 at 100 s, and partial correction of the Doppler background allows the system to remain stable at the 10 −12 -level up to 10 4 s. This architecture significantly reduces optical complexity while providing a robust, high-performance laser source for deployable quantum sensors.
Abstract We demonstrate a laser stabilization based on a spatially-multiplexed, microfabricated rubidium vapor cell. This design integrates multiple optical apertures within a cell, enabling a single input beam to simultaneously capture both Doppler-broadened and saturated absorption spectroscopy signals while a dedicated non-absorbing aperture directs the beam toward the physics package. We achieve a frequency stability of 4 × 10 −13 at 100 s, and partial correction of the Doppler background allows the system to remain stable at the 10 −12 -level up to 10 4 s. This architecture significantly reduces optical complexity while providing a robust, high-performance laser source for deployable quantum sensors.
We propose and experimentally demonstrate a spectroscopic method, named full differential spectroscopy, that uses a single laser beam in retroreflected configuration to manipulate atomic dark states in a vapor cell. Conventional Doppler-free spectroscopy often suffers from limited performance due to the Doppler-broaden background. Here we show that by selectively coupling or decoupling the probe’s polarization components with the pump-induced dark state, we can simultaneously obtain both Doppler-free electromagnetically induced transparency and absorption. A differential signal, with enhanced Doppler-free amplitude and highly suppressed background and noise, is thus obtained. We systematically characterize how polarization angle and light power affect the resonance and noise properties. Using this approach, we stabilize a laser to a rubidium vapor cell, achieving a fractional frequency stability of 1.2 × 10 −13 at 1 s. These results demonstrate a simple, robust route to high-performance optical frequency references and may also benefit quantum sensing or high-resolution spectroscopy.
Vapor-cell spectroscopy is an essential technique in many fields and is particularly relevant for quantum technologies. Most atom- and ion-trapping experiments rely on simultaneous spectroscopy of two atomic transitions, employing a separate apparatus for each transition. We demonstrate simultaneous spectroscopy on two atomic transitions, within a single apparatus, using spatially overlapped beams from two independent lasers. This method enables compact setups and offers superior spectroscopic performance, leading to sharper spectroscopy peaks, stronger absorption signals, and superior laser stability. Doppler-free locking features become accessible over a frequency range several hundred megahertz wider than for standard saturated absorption spectroscopy. Exploring the full parameter space associated with dual-frequency spectroscopy reveals a latticelike structure of sharp resonance features, which enhances experimental versatility by allowing laser frequency stabilization within a wide manifold of locations in two-dimensional frequency space. We present data for 133Cs and 85Rb and compare our results to a theoretical model. Employing the technique for frequency stabilization close to the D2 line of 85Rb results in an improvement in frequency stability by a factor typically between 2 and 3 for averaging times of up to 1 s. The technique will advance portable quantum technologies and facilitate high-precision measurements.
Precise laser stabilization is a fundamental aspect of modern metrology, directly influencing the accuracy of fundamental measurements in fields such as high-precision metrology, atomic sensor applications, and quantum technologies. Saturation absorption spectroscopy (SAS) is one of the most effective techniques for achieving high spectral stability, as it enables laser frequencies to be locked to atomic resonances. This technique exploits the nonlinear interaction between a weaker probe beam and a stronger pump beam within a rubidium (Rb) atomic vapor cell. By eliminating Doppler broadening, SAS allows well-defined hyperfine transitions to be resolved, providing a reliable optical frequency reference. This study aims to optimize laser frequency stabilization using the SAS technique by investigating the effects of laser light polarization, atomic vapor cell temperature, and pump-probe power adjustments. Polarization-dependent selection rules influence transition probabilities, thereby affecting spectral contrast and frequency stability. Additionally, atomic density variations, which depend on the vapor cell temperature, influence signal strength and linewidth, necessitating precise temperature control for optimal performance. Furthermore, the pump power must be sufficient to induce saturation without excessive power broadening, while the probe power must remain low enough to prevent spectral line distortion. By optimizing polarization, temperature, and power parameters, the stabilization of the Rb atomic laser can be enhanced, leading to improved reproducibility and consistency in high-precision measurements. SAS-based laser stabilization is particularly crucial for atomic sensor applications and quantum technologies, where highly stable, narrow-linewidth lasers are essential for precision measurements. Applications such as atomic magnetometers, gyroscopes, and inertial navigation systems depend on precisely stabilized lasers for optimal performance. By enhancing the reliability of laser frequency stabilization, this work contributes to the advancement of next-generation atomic sensors with improved sensitivity and stability.
We implement a compact optical frequency standard scheme with laser frequency locked to the 5 S 1/2 ( F = 2) − 6 P 3/2 ( F ′ = 3) transition of the second excited state of 87 Rb atoms in a 3 mm cubic glass cell, using a Doppler-free saturated absorption spectroscopy. The experimental results show the frequency stability at the level of 2.2 × 10 −12 at 1 s. Furthermore, we conduct an experimental study on the effect of a repump laser on the frequency performance of the saturated absorption spectroscopy optical frequency standard, providing valuable experimental results with reference values for implementing this type of optical atomic clock.
The utilization of atomic or molecular spectroscopy for frequency locking of single-frequency laser to improve laser frequency stability plays an important role in the experimental investigation of optically pumped atomic magnetometers, atomic clocks, laser cooling and trapping of atoms, etc. We have experimentally demonstrated a technique for frequency stabilization of a single-frequency laser employing the bright state spectroscopy (BSS) with a rubidium atomic vapor cell. By utilizing the counter-propagating dual-frequency 795 nm laser beams with mutually orthogonal linear polarization and a frequency difference of 6.834 GHz, which is equal to the hyperfine splitting of rubidium-87 ground state 5S1/2, an absorption-enhanced signal with narrow linewidth at the center of Doppler-broadened transmission spectroscopy is observed when continuous scanning the laser frequency over rubidium-87 D1 transition. This is the so-called BSS. Amplitude of the absorption-enhanced signal in the BSS is much larger compared with the conventional saturation absorption spectroscopy (SAS). The relationship between linewidth and amplitude of the BSS signal and laser beam intensity has been investigated. This high-contrast absorption-enhanced BSS signal has been employed for the laser frequency stabilization. The experimental results show that the frequency stability is 4.4×10−11 with an integration time of 40 s, near one order of magnitude better than that for using the SAS.
Devices based on spectroscopy of atomic vapors can measure physical quantities such as magnetic fields, RF electric fields, time and length, and rotation and have applications in a broad range of fields including communications, medicine, and navigation. We present a type of photonic device that interfaces single-mode silicon nitride optical waveguides with warm atomic vapors, enabling precision spectroscopy in an extremely compact (<1 cm3) package. We perform precision spectroscopy of rubidium confined in a micro-machined, 27 mm3 volume, vapor cell using a collimated free-space 120 μm diameter laser beam derived directly from a single-mode silicon nitride waveguide. With this optical-fiber integrated photonic spectrometer, we demonstrate an optical frequency reference at 780 nm with a stability of 10−11 from 1 to 104 s. This device harnesses the benefits of both photonic integration and precision spectroscopy for the next generation of quantum sensors and devices based on atomic vapors.